Protesters in New York have found innovative ways to deal with water used to clean dishes.

LOS ANGELES (AP) -- With thousands of Occupy Wall Street demonstrators roughing it in parks for up to six weeks, garbage, human waste and hygiene are becoming a growing worry in public encampments nationwide.

Poor food storage exacerbated a rat infestation in Oakland. Inspectors found open human waste in Philadelphia. Hypothermia cases developed in Denver after a snowstorm hit.

Disease is the chief concern with so many people living in close proximity without proper sanitation.

"Any time you have a large number of people in an event like this, there's potential for illness to spread rapidly," said Angelo Bellomo, director of environmental health for Los Angeles County. "Conditions can change within an hour or two."

Poor food storage, along with public urination and defecation, led Oakland police to dislodge 200 protesters from a plaza outside City Hall before dawn Tuesday.

In Philadelphia, sanitary conditions have worsened at the 350-tent Occupy Philly camp, said city managing director Richard Negrin. The camp has four portable toilets that have not been cleaned or emptied regularly.

Health officials, who conduct daily inspections of Los Angeles' camp, have directed organizers to dispose of wastewater from portable showers into drains rather than the ground, and to increase the number of portable toilets, have them emptied twice a day and provide water jugs for hand-washing.

Close-quarters living can facilitate the spread of germs through airborne, foodborne or person-to-person contact. Norovirus has caused outbreaks of gastroenteritis on cruise ships, for example, while adenovirus has caused influenza and other respiratory illnesses in military barracks.

So far, no outbreaks of illness have been reported from the grassroots demonstrations that have sprouted nationwide to oppose policies viewed as promoting corporate greed. Medical tents in Los Angeles have only treated minor ailments such as scrapes and colds.

Protesters in Denver, however, said they took two demonstrators to a hospital with symptoms of hypothermia during an snowstorm that started Tuesday night.

Some demonstrators complain that the health issues have been exaggerated as a pretext to crack down on the camps. Authorities did not seem to be concerned about unhygienic conditions that existed before, they said.

"They never go and clean up Skid Row," said Juan Alcala, a camper in Los Angeles, where more than 350 tents are jammed on a lawn around City Hall.

The protesters are taking pains to keep the premises clean but acknowledge it's an ongoing battle to keep up as tents proliferate and attract the attention of public health officials.

Mayor Antonio Villaraigosa told the Los Angeles Times that county health inspectors have expressed concerns over the cleanliness of the camp. The mayor also said the city's lawn and trees are suffering.

"The lawn is dead, our sprinklers aren't working ... our trees are without water," Villaraigosa told the Times.

Although protesters formed a sanitation committee from the start, hygiene issues have gotten more complicated than Occupy LA organizers anticipated.

The camp is largely well kept, although numerous trash bins around the site were overflowing during recent visits. Organizers pay a private hauler $57 a week to collect the rubbish daily after being fined by the city for failing to remove trash.

As the scent of marijuana wafted in the air and drumbeats sounded in a steady rhythm, organizers roamed the camp, urging people to pick up their trash and not to walk barefoot. Most people complied and some pitched in. Alcala seized a large palm frond and swept concrete walkways.

Protesters said overall, people were careful about rubbish. "I smoke and I'm really conscious about not throwing my butts on the ground," said another camper, John Waiblinger.

Personal hygiene has been a more difficult issue.

Many people use showers at homeless shelters in Skid Row, while some have organized bathing trips to homes, said organizer Gia Trimble.

Others said they used the camp showers on site, filling up a plastic bag with solar-heated water or hot water from a City Hall faucet. The bag, which has a tube to spray the water, hangs from a cord.

"I use the solar-heated shower or even those moist towelettes," Alcala said. "We're clean here."

Campers said they weren't worried about illnesses. Nevertheless, some were taking commonsense precautions.

Tommy Schacht, who was brushing his teeth with bottled water on a recent morning, said he goes home to shower and change clothes, and mostly used bathrooms at nearby businesses or public facilities instead of the portable toilets on site.

"I don't worry about that at all, but I try to stay away from people that are dirty," he said.

Some campers' clothing was visibly grubby, although others said they went to friends' homes or Laundromats to do laundry.

Food handling has posed other problems.

The camp shut down its food tent, where volunteers made everything from sandwiches to a tabouli-type salad in blenders, after inspectors noted that it was not in compliance with food handling laws.

Now, donated prepared foods, ranging from cookies to packaged sandwiches, are distributed. Most campers make their own meals, heating up Ramen noodles, canned soup and refried beans on small gas-powered camp stoves.

Schacht, who's been camping out for more than a week, said he was cooking lots of pasta - "anything that can be made with hot water, that's easy."

Organizers said that although they continue to hammer out unforeseen logistical issues, they're trying to keep the political cause paramount.

"It's a very interesting time for us. We're dealing with trying to become self-sufficient," said Trimble. "We don't want the focus to be on their living conditions, we want it to be on the movement."